<html lang="zh">
<head>
    <meta charset="UTF-8">  
    <title>变量-布尔类型</title>
</head>

<body>
</body>
<script>
    var str="hello world"
    //非空字符进行布尔判断时会被理解为布尔值true
    if(str){
        alert("值为真");
    }
</script>

</html>